The present invention relates generally to a method for producing packages with integral security tags of the RF-EAS type. More particularly, the invention relates to such a method whereby the security tags are applied to a web of packaging material that is converted into packaging blanks (e.g., trays, lids, cartons, containers or the like) on a printing press in a single pass operation, at substantially the same time that sales graphics are printed on the blanks. In addition, the present invention includes a procedure for precisely tuning the resonance frequency of the tags by adjusting print register for optimum performance in the field.
RF-EAS (Electronic Article Surveillance) tags are passive circuits with a resonance frequency tuned to the frequency of tag detectors located at the entrances and exits of retail establishments. When an active tag passes through a detector, an alarm sounds, alerting store employees to the potential theft of the tagged merchandise. State of the art RF-EAS tags are generally produced by a number of steps which include stamping, masking, photochemical treatments, chemical etching and printing. However, the tags currently available are too expensive to be economically used on items retailing for about $5.00 or less. The use of currently available tags entails not only the cost of the tag itself, but the cost of application of the tag to the product or its package, either on a packaging line, in a warehouse, or in the retailer's stockroom. Examples of such prior art tags are disclosed for example in U.S. Pat. Nos. 4,583,099; 4,835,524; 5,442,334; and, 5,574,431. As disclosed in these patents, such tags are generally prepared by applying patterned paths of conductive material on both face surfaces of a substrate, e.g., an inductor element (L) and capacitor element (C) on opposite sides of a suitable dielectric substrate.
It has also been suggested, as shown for example in U.S. Pat. No. 5,781,110, to form such tags on one side of a substrate utilizing a combination laminating printing procedure. However, these devices have been found to be inadequate in use because they do not resonate sharply enough to be detected by conventional and widely distributed detectors. Moreover, no means is provided for controlling the resonance frequency of such tags. Thus there remains a need in the art to provide a reliable and tunable security tag at reduced costs. The present invention fulfills that need by providing an RF-EAS tag that can be applied directly to the package component during the manufacturing process, eliminating the need for separate application, and which can be precisely tuned for controlling the resonance frequency.